Evaluation of Soy Lecithin and Soy Oil in the Diet of L. vannamei
World shrimp production has been increasing for the past four decades. In 2004, production reached over 6 million tons. This unprecedented expansion has been primarily attributed to increased production from the shrimp farming activities. In 2004, more than 41% (2.5 million tons) of the world’s total shrimp production was from farming. The primary cost of production in shrimp farming is feed, with protein being the most expensive macronutrient in these diet formulations. Although marine fish meals and fish oils provide excellent sources of high quality essential amino acids, lipids, vitamins, minerals and attractants in aquaculture diets, we must consider the finite availability these resources and the impact their procurement has on the environment. In addition, demand for fishery products from other high profit sectors, such as the pet food industry, will force fish meal prices up until its usage in aquatic feeds will no longer be economically feasible. If aquaculture is to continue to be an increasing contributor to the human food supply, it is critical that aquaculture feeds become less reliant on marine fisheries products. Due to both economic pressures from high fish meal and fish oil prices and pressures from buyers and consumers requiring sustainable practices, the use of high levels of fish meal and fish oils is no longer acceptable. Currently, feed mill manufacturers and producers are taking a pragmatic approach by looking into practices that will not only reduce feed production costs, but also improve their public image. Increasing the use of soybean meal and other soy products in shrimp diet formulations should reduce feed costs and improve both the image and sustainability of this growing industry.
This study was part of a continuing project focusing on developing plant-based feeds for aquaculture; the current work was geared toward enhancing the lipid component of plant-based feeds. A systematic, stepwise approach has been developed to produce good scientific data and to ensure that larger scale pond based trials can follow with the highest potential for success. The ultimate goal of the research was to provide adequate information to the feed formulators to allow them to use the maximum level of soy products (soybean meal, soybean oil, and soy lecithin) in their feed formulations.
Previous studies have shown that fish meal can be replaced either singularly with animal by-product meal or in combination with plant protein sources without affecting the physical and nutritional quality of the feeds. However, the use of alternative protein sources is often done in combination with the use of marine oils to supply essential fatty acids and enhance the palatability of the diet. Soybean meal has been identified as a good alternative protein source due to its high protein content and relatively balanced amino acid profile. In previous studies we have maximized the use of soybean meal in shrimp feeds, however, there are numerous other products derived from soybeans that can be utilized in aquaculture diets including soy oil and soy lecithin which have yet to be optimized. Although it is unlikely that soy oil will be suitable as a complete fish oil replacement due to a lack of essential fatty acids, it may be possible to reduce fish oil use in plant-based shrimp feeds by diluting fish oil with soy oil. Another approach to enhancing the lipid component of plant-based feeds is the inclusion of soy lecithin. Phospholipids play an important role in maintaining cellular structure. They also enhance cholesterol transport, increase lipid retention, and may facilitate the pelleting process by acting as a lubricant. Soy lecithin, a primary source of phospholipids, has the potential to improve the lipid component of plant-based feeds.
The objectives of this study were: 1. To evaluate the response of Pacific White Shrimp to diets with increasing levels of dietary lecithin (0-2%) in conjunction with decreasing levels of fish oil to maintain the same dietary lipid level, 2. To evaluate the response of the shrimp to diets with decreasing levels of fish oil supplemented with increasing levels of soybean oil to maintain the targeted lipid content.